DESCRIPTION (Taken from abstract): A number of studies have informed us about the substantial risk for HIV associated with chronic homelessness among youth in both the U.S. and Australia, even though these studies have typically been cross-sectional or samples of convenience. To understand the high seroprevalence rates among older homeless youth, the developmental trajectories into and out of risk for HIV and homelessness can best be understood from longitudinal studies of First Time Runaways (FTR). Among these youth contextual factors (the national, community supports, street experiences, peers, and family) that influence these trajectories can be identified and observed over time. To obtain a contrast for the policy and provider context, comparisons between FTR in Australia and the U.S. are proposed. Australia differs from the U.S. in policies of harm reduction, needle exchange, national programs for positive sexual health, and the organization and distribution of community resources for homeless youth. A representative sample of FTR will be recruited in LA, CA and Melbourne, Australia (n=480) stratified by gender (120 males & 120 females per city; aged 11-17 years). Across cities, information will be collected at recruitment, 3, 6, 12, 18, 24, 30, and 36 month intervals from youth regarding four domains: 1) the individual's risk for HIV (substance use & sexual behaviors) and chronic homelessness; 2) street experiences (daily activities, survival strategies, violence, delinquent acts and school/employment patterns) and personal resources (social identifiers, goals, coping styles, psychiatric distress); 3) the contest of the peers' risk acts and community factors (e.g. service provider, policy factors, and informal networks) that influence youth's response to becoming homeless; and 4) background characteristics of the youth and their families. To further understand the social and structural context of youth's HIV-related developmental trajectories, the empirical assessments of the FTR will be complemented by qualitative case descriptions gathered from three additional sources: 1) annual empirical assessment of samples of Experienced Runaways (three cross-sectional samples gathered annually, n=200 per city), in order to describe differences in the culture of homelessness over time and the drift over time in the similarity/differences between Experienced Runaways and FTR; 2) case studies of HIV-related policies and service providers for runaways in each city (n=20); and 3) qualitative interviews of a subset of FTR regarding their social networks (n=25/city). The results will be used to design interventions for FTR to reduce their risk for HIV and for providers who may influence their trajectories into increasing or decreasing risk for HIV and becoming chronically homeless.